This invention relates to the processing or treatment of fluids in such operation as mass transfer, heat transfer in heat exchangers, liquid-gas contacting, and separation of contaminant particulate, mist and fumes from gases. This invention has particular relationship to such treatment of fluids with an array of sets of elements in rows with elements in any row being staggered with respect to the elements in adjacent rows.
An array of such elements may be used as a separate unit, or a plurality of arrays may be disposed in series in a tower which serves for mass transfer between a gas and a liquid. The word "element" as used in this application means an element, usually an elongated element, of any transverse cross-sectional shape. The word "element" includes within its meaning cylindrical elements which are hollow or solid such as tubes or rods. Cylindrical elements have advantages in the treatment of fluids. The word "cylindrical" is used here in its broad sense. A cylinder is defined as a three-dimensional surface formed by tracing a plane continuous closed curve with a line perpendicular to the plane of the curve.
Staggered tubular arrays have been used for various industrial purposes. For example, in cross-flow heat exchangers, fluid to be heated or cooled flows perpendicularly to a staggered-tube array in which the tubes are arranged in a triangular pitch or rotated-square array. Typical values of tube pitch for common heat-exchanger tube layouts are given on pages 10-26 of Chapter 10, "Thermal Design of Heat-Transfer Equipment", in Perry's Chemical Engineers' Handbook, 5th Edition, McGraw-Hill (New York). Similar staggered tube or rod arrays have also been employed for gas cleaning and mass transfer.
Gas demisting and particulate-removal applications of arrays of cylindrical impingement rods of elliptical and streamlined transverse cross-section are described in British Pat. Nos., Talboys 562,593, General Dynamics 897,417 and Lerner 1,594,524. British Pat. No. 644,391 describes a particulate filter comprising a staggered array of elements of streamlined transverse cross-sectional shape fabricated from perforated sheet or gauze. Talboys discloses an array of spaced parallel tubes for removing dust and impurities from air in which the tubes are perforated or foraminous and are covered with sleeves of woven cloth which are kept wetted with oil. These tubes are of cylindrical or elliptical transverse cross-section. General Dynamics discloses a mist-eliminator array of impingement rods of streamlined transverse cross-section covered with a water-absorbant material. Lerner describes the application of a staggered array of fibrous cylinders for gas absorption, mist and particulate removal. Andersen, in U.S. Pat. No. 3,447,287, discloses an incinerator scrubber containing a horizontal array of staggered rows of porous refractory cylindrical impingement piers oriented perpendicularly to the path of gas flow. Ekman, in U.S. Pat. No. 3,795,486, describes a wet scrubber comprising a horizontal array of rod-like elements for absorbing sulfur oxides. Staggered arrays of other types are shown in Heenan & Froude, French Pat. No. 531,515. The instant invention concerns itself with, and is applicable to, the arrays disclosed in the above-described patents and literature which are typical of the prior art.
In most, if not all, of the above-described applications of staggered arrays of elements, the elements in the rows are spatially separated from each other and from the elements of the adjacent rows so that open flow space completely surrounds each element. A disadvantage of the prior-art staggered arrays is that they are not fully effective or efficient in the treatment or processing of the fluids which are passed through them. Heretofore, the cause of this deficiency in effectiveness and efficiency has not been realized or known. Staggered element arrays are usually so arranged that from the fluid approach point, or direction perpendicular to the array, the fluid "sees" nothing but element surface, i.e., there is no open, unobstructed flow area on a projected view. The conventional wisdom on which such an arrangement is based is that all fluid will impinge on, flow around, and contact each element. While this is the desired and desirable objective, it has not been realized in the prior-art open array arrangement of elements.
It is an object of this invention to overcome the disadvantages of the above-described prior art and to provide treatment or processing apparatus for fluids, including a staggered array of elements, in whose use the treatment shall be effectively and efficiently carried out.